Transparent film dressings are widely used as protective layers over wounds because they facilitate healing in a moist environment while acting as a barrier to contaminating liquids and bacteria. The films are also used as surgical drapes because of their barrier properties. Dressings and drapes fitting the above description are available under a number of trade names such as TEGADERM.TM. (3M Company, St. Paul, Minn.), BIOCLUSIVE.TM. (Johnson & Johnson Company, New Brunswick, N.J.), OP-SITE.TM. (T. J. Smith & Nephew, Hull, England), and UNIFLEX.TM. (How Medica, Largo, Fla.).
The polymeric films used in those dressings and drapes, referred to as dressings below, are conformable, i.e., the films are extremely thin, flexible and supple. They are typically supplied with a releasable protective liner covering the adhesive coated surface of the film. When the liner is removed, the adhesive coated film tends to wrinkle and adhere to itself, interfering with the smooth, aseptic application of the dressing to a patient's skin. Various delivery systems have been proposed to address this problem.
One known delivery system is described in U.S. Pat. No. 4,485,809 in which a dressing is attached to a release liner by the use of adhesive between the dressing and the liner. The liner material functions as a frame to provide support during placement of the dressing after a center section of the release liner has been removed. After the dressing has been affixed, the frame is removed from the dressing by tearing the film along perforations provided around the center section. Because the center section functions as a liner, however, it cannot be removed until immediately before the dressing is placed on a patient. Furthermore, because the frame must be torn from the perimeter of the dressing, the adhesive bond between the skin and the dressing is often disturbed, which can then lead to premature failure and removal of the dressing by bed linens and other means.
U.S. Pat. No. 4,600,001 also describes a delivery system which includes a pair of opposed strips and a delivery layer which is heat laminated to the film. In use, a release liner is removed from a dressing, the dressing is placed on a patient, the delivery means layer is then removed from attachment with the film. After the film is secured on a patient, the opposed strips and film attached to them are removed using perforations in the film. In this device, the delivery means layer is preferably transparent or translucent to allow viewing through the dressing during placement. Like the dressing described above, the tearing of the film to remove the opposed strips can disturb the adhesive bond between the skin and the dressing, again leading to premature failure.
Carrier-type delivery systems offer an alternative delivery system for use with conformable thin films. The use of a removable carrier, which does not require tearing of the film after it has been placed on the patient, avoids the problems described above. Furthermore, a center portion of the carrier is preferably removable thus forming a frame which allows one to view the attachment site on a patient through the film exposed within the frame. The frame-type carrier aids in accurate placement of the dressing on a patient.
EPO Publication No. 0 051 935 describes a removable frame delivery system for thin polymeric film dressings. In that delivery system, the bond between the frame material and the film is mechanical in nature and is formed when the film is extruded onto the frame material. Dressings according to this reference are manufactured with a central window which is control depth die cut in the frame material. In use, the die cut window is first removed from the center of the frame, after which the release liner is removed from the adhesive layer and the dressing is placed on a patient. The frame is then removed from the film leaving the dressing in place on the patient.
One drawback associated with dressings manufactured according to EPO Publication No. 0 051 935 is the limited amount of control a manufacturer may exercise over the strength of an extruded or mechanical bond. To facilitate placement of the dressing, EPO Publication No. 0051935 teaches that the tenacity of the bond between the film and the frame material must be greater than the tenacity of the bond between the film and the liner. Extruding allows a manufacturer limited control over the tenacity of a bond.
U.S. Pat. No. Re 33,727 also describes a frame type delivery system including a composite with a thin polymeric film and a pressure-sensitive adhesive coated on one surface of the polymeric film. A release liner is attached to the adhesive coated surface of the film and a frame is attached to the exposed surface of the film opposite the surface to which the adhesive has been applied. When applied, the release liner is first removed from the adhesive coated surface, the film and frame are then placed on a patient and the frame is then removed from the film, which is left on the skin.
U.S. Pat. No. Re 33,727 does not discuss the mechanism by which the frame is bonded to the film, nor does it discuss the problems associated with removing the central window without disturbing the bond between the frame and the film. The patentee in Re 33,727, however, relied on label construction for enablement which used either pressure sensitive adhesives or a radiation-curable film to bond layers of a composite together. In this regard, such frame delivered dressings according to the above references contemplate the extrusion or radiation curing of the thin film directly on the carrier material.
A low adhesion coating on the top face of the dressing provides the ability to apply and remove tapes and other devices over the dressing, thereby enabling the dressing to be used as a platform for those tapes and other devices. The low adhesion coating allows the tapes and other devices to be removed without also removing or disturbing the underlying dressing and allowing additional contamination to reach the wound. An example of such a dressing is TEGADERM.TM. No. 1620 dressing available from 3M Company, St. Paul, Minn.